1. Field of Invention
The present invention relates to packaging cases that encase electro-optical devices, (hereinafter “packaging case-encased electro-optical device”), as well as the electro-optical devices themselves. In other words, the invention relates to an electro-optical device that is packaged or housed in a packaging case. Such electro-optical devices include liquid crystal panel used as a light valve for a projection type display device, such as a liquid crystal projector. The invention further relates to a projection type display device including the packaging case-encased electro-optical device.
2. Description of Related Art
Generally in the related art, when a liquid crystal panel is used as a light valve in a liquid crystal projector, high-intensity source light from a light source, such as a metal halide lamp, enters the liquid crystal panel in a gathered state to perform extended projection onto a screen. When the high-intensity source light enters in this manner, the temperature of the liquid crystal panel rises. The temperature of liquid crystals sandwiched between a pair of transparent substrates in the liquid crystal panel rises as well, which causes the property of the liquid crystals to be deteriorated. In addition, when the source light, particularly, has unevenness, the liquid crystal panel is partially heated to generate a so-called hot spot, and irregularities are generated in the transmittance of the liquid crystals to degrade the image quality of projected images. Such a temperature rise is relaxed more or less by disposing a heat ray cut filter between the light source and the liquid crystal panel to reduce unnecessary incidence of infrared rays, or by cooling the liquid crystal panel by air or liquid. However, to intend to form high quality images, more efficient schemes to reduce or prevent temperature rise are needed.
The related art has attempted to address or solve this problem via various schemes, including: to dispose a dust-proof glass on both sides or one side of the liquid crystal panel; to dispose a light blocking film over a substrate on the light incident side of the liquid crystal panel; and to form a packaging case made of a light reflective material, such that the packaging case has the liquid crystal panel packaged or housed therein. According to these schemes, the temperature rise in the liquid crystal panel can be reduced or suppressed properly. More specifically, when the dust-proof glass is disposed, it is expected to serve as a heat sink for the liquid crystal panel. The light blocking film and the packaging case formed of the light reflective material reduce or suppress the source light to excessively enter the liquid crystal panel, and thus the action of converting the light to heat can be reduced or suppressed inside the liquid crystal panel.
However, the above-described schemes to reduce or prevent the temperature rise in the liquid crystal panel are subject to the following problems. First, there are no perfect schemes to reduce or prevent the temperature rise in the liquid crystal panel in general. In other words, as long as the high-intensity light from the source light is projected, the problem of the temperature rise in the liquid crystal panel always inevitably exists. In order to enhance the image quality, the problem is always challenging. In short, the schemes to reduce or prevent the temperature rise in the liquid crystal panel are not satisfactory, and more effective schemes would be advantageous.
Furthermore, each of the above-described schemes to reduce or prevent the temperature rise are subject to disadvantages as described below. First, in the scheme to dispose the dust-proof glass, materials that could serve as the heat sink are generally expensive, causing increases in fabrication costs and product costs. Effectively reducing or preventing the temperature rise in the liquid crystal panel utilizing only this method is difficult.
Moreover, in the light reflection schemes by the light blocking film and the packaging case, the amount of light reflected is increased when their areas are expanded. Thus, the temperature rise in the liquid crystal panel can certainly be reduced or prevented. However, when the amount of light that is reflected is unnecessarily increased, the stray light in a housing to accommodate the packaging case-encased liquid crystal panel is increased, which can adversely affect the image quality. Besides, the amount of the source light that is supposed to enter and pass through the liquid crystal panel is to be reduced as the area of the light blocking film is expanded more and more, which can darken images. The above impedes bright images from being displayed with the use of high-intensity source light. As described above, the various schemes are also subject to a disadvantage in that they do not solve the problems drastically.